I'd get the non-retina. why?
1. i agree, the portability of the retina is a nice feature. but the 15" mbp is still portable enough for university. seriously, go to the apple store and try it out. the retina is thinner, but it's still bulky, no question.
2. you're a college student. if anything goes wrong with the retina, you're screwed. why? because to replace any single component of the retina, you need to replace the ENTIRE logic board. this will cost $1000+
3. the retina screen is nice, but at least for now, nothing is customized for it. web pages will appear blurry, images will be blurry, etc.
4. if you plan to do audio/video editing, you need lots of storage. there are lots of problems with external drives (portability being a big problem). you could just get the normal mbp with 1 TB hdd
5. if you get the non-retina mbp, it doesn't cost a fortune to upgrade and repair. want to get a new battery? It's going to cost $199...
basically, i'd avoid listening to the advice you see on this forum. i can't believe everyone's telling you to get a retina mbp, when it's not suited to your needs. a lot of people are caught up in the hype
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if you use Logic, you will need a lot of *local* storage for samples, VSTs, expansions, and everything else. in 4 years, you will definitely need more than 250 GB (maybe even more than 1 TB). the problem with the retina is that you simply can't get more space.
and running these from an external HDD will have tons of lag, unfortunately